A primary use of computers, especially personal computers, is "word processing." Word processors have replaced the typewriter as a principal means for document production. A word processor allows a user to input the text of a document, such as a letter, into a computer. Once the document is in the computer the user can make revisions to it. For example, paragraphs can be easily moved around, misspelled words can be corrected, and words can be deleted. Finally, the document can be printed out or can be stored in the computer for retrieval and updating at a later date. One such word processor is Microsoft Corporation's WORD.
In producing documents, it is typically very important that each word in the document be spelled correctly. In manual word processing systems (e.g., the typewriter), the only way to check the spelling is to manually review the document after it is typed. In computer word processors, a spell checking program (spell checker) is often used to check the spelling of the words in a document. A spell checker has an associated dictionary file that contains a list of correctly spelled words. To check the spelling of a word in the document, the spell checker searches the dictionary for that word. If the word is in the dictionary, then the word is correctly spelled. Otherwise, the word is misspelled. (Since a dictionary will not contain every possible word, e.g., last names, it may be that the word is correctly spelled but not in the dictionary.) The spell checker typically reports the misspelling to the user and prompts the user for the correct spelling. The spell checker then replaces the misspelled word with the correctly spelled word.
The typical spell checker also allows the user to add words to the dictionary. For example, the dictionary may not include terms that are used in specialized fields, such as medicine or law.
A common problem in the entry of words occurs when a word is consistently misspelled in the same way. For example, the user may type "teh" rather than "the." Or the user may type "supercede" rather than "supersede." A typical spell checker will detect each misspelling and give the user a chance to correct it. However, the next time the user misspells the word in the same way, the user must reenter the correct spelling. This continual need for correction is undesirable. It would be desirable to have a spell checker in which these misspellings could be automatically corrected.